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1.
Veena U. Joshi 《Journal of the Geological Society of India》2018,91(5):554-562
Soil erosion by water has been a major problem since man introduced agriculture in the landscape. Soil erosion is a common hazard which is steadily increasing as a result of human activities in many parts of the world. Hunter Valley of NSW is located in subtropical eastern Australia. The region is known for its diversity in landscape that includes wide floodplains, extensive estuarine wetlands, undulating country, escarpments and rugged sandstone gorges. The region is also well known for wine production. The Hunter Valley has a long history of soil erosion following the European settlement 150 years ago. Currently there have been renewed human activities in the south central part of the region for coal mining, leading to clearance of vegetation and disturbance of soil. The present study addresses the issue of soil erosion in a part of Hunter Region by employing the Revised Universal Soil Loss Equation (RUSLE, Renard et al., 1977) model. The results indicate that the average annual soil loss from the area is 0.7 kg/m2/year, which is well beyond the tolerance limit of the soil. Statistical relationships between soil loss and each parameter of the RUSLE equation were obtained and it was found that C factor has significant influence on the average soil loss in the area. An overall picture that emerges out of the study is that the region is continuing to suffer as a result of disturbance in natural environment from the historical times till present. 相似文献
2.
Veena U. Joshi 《Journal of the Geological Society of India》2014,83(6):613-624
Nearly 4 million hectares of land in India is affected by rill and gully erosion. It is a severe form of soil erosion rendering vast tracts of lands into wastelands giving rise to the formation of badlands. Rate of land degradation through gullying is triggered recently due to the ill-advised landuse practices all over the country. The study area represents one such badland locality along the banks of Pravara river and two of its tributaries in the Deccan trap region, Maharashtra. The area is extensively reclaimed in the last two decades for agricultural practices. The rates in the cross profile changes as well as land lowering were measured with the help of a self fabricated micro-profilometer and erosion pin method. Five first order gullies were monitored using the micro-profilometer. Results of the micro-profilometer technique reveal considerable changes in the cross-sectional areas of individual gullies in this area, which shows the dynamic soil removal mechanism operating in this region. In addition to this, two well developed gully catchments were surveyed using a theodolite and erosion pins were installed in these basins in May 2007. After one year, the exposed pinheads were measured and net gain and net loss in the volume of the sediments were calculated for both the basins. The same practice continued in May 2009. After two years of monitoring the sediment yields were calculated. Average of these two years indicates an annual sediment yield of 1.79 kg/m2 for sample basin 1 and 0.76 kg/m2 for sample basin 2. The calculated yield was compared with the threshold values of soil tolerance limits and it was found that the area has crossed the threshold limit of soil tolerance. 相似文献
3.
The main objective of this study is to measure the effect of slope and grass-cover on infiltration rate, run-off and sediment
yield under simulated rainfall conditions in a badland area located in the upper Pravara Basin in western India. An automatic
rainfall simulator was designed following Dunne et al (1980) and considering the local conditions. Experiments were conducted on six selected experimental fields of 2 × 2m within
the catchment with distinct variations in surface characteristics — grass-covered area with gentle slope, recently ploughed
gently sloping area, area covered by crop residue (moderate slope), bare badland with steep slope, gravelly surface with near
flat slope and steep slope with grass-cover. The results indicate subtle to noteworthy variations amongst the plots depending
on their slope angle and surface characteristics. An important finding that emerges from the study is that the grass-cover
is the most effective measure in inducing infiltration and in turn minimizing run-off and sediment yield. Sediment yields
are lowest in gently sloping grass-covered surfaces and highest in bare badland surfaces with steep slopes. These findings
have enormous implication for this area, because over 2/3 area is characterized by bare and steep slopes. 相似文献
4.
G. R. Lakshmana Rao Y. Veena Devi K. G. Reddy 《Theoretical and Applied Climatology》1987,38(3):147-150
Summary The dominant surface energy budget parameters, namely the net radiation fluxes, must be precisely known for an understanding of southwest monsoon behaviour and the early stages of formation of a meteorological system, i.e. trough, low pressure, depression, cyclone etc., and break monsoon conditions over the Bay of Bengal region. The data measured during the MONEX-79 period from July 16–31 are used in order to study the fluctuations of energy fluxes and the net radiation in the month of July over the region. During this period the total energy flux is increasing from South to North with a maximum over the head of the Bay. However, the fluctuation of net radiation is not significant. There is an outstanding increase in the energy flux with anomalies of values 240 W/m2.
With 2 Figures 相似文献
Zusammenfassung Für das Verständnis des Südwestmonsuns und für die Entwicklung eines meteorologischen Systems, wie Trog-Tiefdruck-Depression-Zyklone etc., sowie für die Bedingungen des Monsunendes über der Bengalischen Bucht, ist das genaue Wissen um die wichtigen Parameter der Energiebilanz an der Oberfläche, insbesondere der Strahlungsbilanz und der anderen Energieflüsse, unverzichtbar. Die Beobachtungsdaten vom 16.–31. Juli während MONEX-79 werden zum Studium der Energieflußfluktuationen und der Strahlungsbilanz für Juli in diesem Gebiet herangezogen. In dieser Periode nahm die Energieflußsumme nach Norden zu, mit einem Maximum über dem nördlichsten Teil der Bucht, während die Fluktuation der Strahlungsbilanz unbedeutend blieb. Trotzdem zeigt sich eine bedeutende Erhöhung des Energieflusses von bis zu 240 W/m2.
With 2 Figures 相似文献
5.
Abhay Anand Bourai Sunita Aswal Anoop Dangwal Mukesh Rawat Mukesh Prasad Nagendra Prasad Naithani Veena Joshi Rakesh Chand Ramola 《Acta Geophysica》2013,61(4):950-957
Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. 222Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then 222Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq·m?3 with geometrical mean value of 302 ± 84 Bq·m?3. Th significance of this work is its usefulness from radiation protection point of view. 相似文献
6.
Veena Joshi Devidas Tambe Gorakh Dhawade 《Journal of the Geological Society of India》2009,73(3):355-370
One of the most serious limitations in studying the surface morphometry of a badland landscape is the nonavailability of a
very fine resolution data which is essential for such types of studies. Local relief of most of the badlands in India and
also from other parts of the world exhibit limited relief amplitude, often within a few meters. The paper reports a case study
carried out in a riverine badland formed along the Western Deccan Trap Region. An attempt has been made in the present paper
to extract the morphometric variables of the landscape from the DEMs derived from a high resolution field generated data,
because the accuracy of the DEM derived values are dependent on the pixel resolution of the DEM from which they are generated.
The size of the pixel resolution should be fixed differently for different landscapes depending on the landscape process in
the area. The local relief of the area is around 10 m and for such types of landscapes the topographical maps and also the
web-available DEMs are of very coarse resolutions which are not suitable for the analysis. Therefore two well defined tributary
catchments were chosen from the area under investigation and theodolite surveys were carried out, contours were generated
with 10 cm interval, DEMs were derived by using Arc GIS software. SRTM (Shuttle Radar Topography Mission) 90 m resolution
data were utilized to generate DEM for the whole basin. Hypsometric and the drainage basin parameters were extracted from
these data by using the same software. Fractal dimension of the whole basin and the sample basins were also obtained for the
same data. The morphometric data generated were used to understand the geomorphic processes operating in the area. 相似文献
7.
Veena U. Joshi 《Journal of the Geological Society of India》2009,74(6):711-722
Quartz sand grains obtained from a deeply gullied topography along the banks of two tributaries of River Pravara in Godavari
Basin, Maharashtra have been examined with a scanning electron microscope (SEM) in order to make the environmental interpretations
of these deposits. The sediments reveal features resulting from mechanical grinding as well as from chemical alteration. Conchoidal
fractures, cleavage planes, grooves, v-shaped indentations etc are the mechanical features documented on the grains whereas
solution pits of varying sizes and intensity, precipitation surfaces, oriented v-pits, solution crevasses and etching are
the features of diagenetic origin. Few sand grains show the evidence of wind transported sediments. Several evidence indicate
that the samples have undergone digenetic changes. Few grains exhibit the features of intense chemical breakdown. The overall
assemblages of the grain surface features suggest that the samples have been subjected to subaqueous transport for a considerable
period of time. The chemical features such as etching, solution pits or semi circular arcuate steps that are found in abundance
in these grains are due to the dissolution of the sediments in a low energy fluviatile environment, such as in floodplain
region. 相似文献
8.
The Deccan Trap region exhibits an erosional landscape over a relatively ancient and stable Deccan shield. The Quaternary history of the area has been reconstructed on the basis of evidence from alluvial deposits occurring along the major rivers. However, recent investigations have revealed that evidence for geo-environmental change during the Quaternary Period is also contained in the colluvial deposits that occur in the foothill zones. The colluvial deposits, ranging in thickness from 1 to 10 m, invariably occupy gently inclined pediment slopes. The sediments are presently deeply dissected by gullies, and the process of colluviation has almost ceased. These deposits are best preserved in the semi-arid parts of the region. Detailed textural, geochemical and stratigraphical studies at four different sites reveal similar input processes, the slight variations being attributed to local environmental factors. Scanning electron microscopy studies of some grains indicate marginal contribution of aeolian processes at the time of deposition. Mesolithic artefacts and a few U/Th dates indicate that the colluviation took place during the Late Quaternary. The properties of the deposits suggest relatively high energy conditions as well as a remarkable variability in the intensity of hillslope processes. These properties are indicative of semi-arid conditions during which the regolith was stripped from devegetated hillslopes and was deposited on the pediments. A variety of evidence indicates that the period of colluviation coincided with arid conditions during the Last Glacial Maximum. The geomorphological and archaeological evidence also indicates that incision by gully systems was initiated during the early Holocene humid phase. The environmental conditions deduced for the study area are similar to those reported for other parts of the intertropical zone. © 1997 John Wiley & Sons, Ltd. 相似文献
9.
Veena Srinivasan Karen C. Seto Ruth Emerson Steven M. Gorelick 《Global Environmental Change》2013,23(1):229-239
While there is consensus that urbanization is one of the major trends of the 21st century in developing countries, there is debate as to whether urbanization will increase or decrease vulnerability to droughts. Here we examine the relationship between urbanization and water vulnerability for a fast-growing city, Chennai, India, using a coupled human–environment systems (CHES) modeling approach. Although the link between urbanization and water vulnerability is highly site-specific, our results show some generalizable factors exist. First, the urban transformation of the water system is decentralized as irrigation wells are converted to domestic wells by private individuals, and not by the municipal authority. Second, urban vulnerability to water shortages depends on a combination of several factors: the formal water infrastructure, the rate and spatial pattern of land use change, adaptation by households and the characteristics of the ground and surface water system. Third, vulnerability is dynamic, spatially variable and scale dependent. Even as household investments in private wells make individual households less vulnerable, over time and cumulatively, they make the entire region more vulnerable. Taken together, the results suggest that in order to reduce vulnerability to water shortages, there is a need for new forms of urban governance and planning institutions that are capable of managing both centralized actions by utilities and decentralized actions by millions of households. 相似文献
10.
Application of Universal Soil Loss Equation (USLE) to recently reclaimed badlands along the Adula and Mahalungi Rivers,Pravara Basin,Maharashtra 总被引：1，自引：0，他引：1
The rapid erosion of soil by wind and water has been a problem since man began cultivating the land. Moreover soil erosion, as a hazard, has always been associated mainly with agriculture in the tropical and semi-arid areas. Soil loss through rill, gully and sheet erosion is a major environmental problem in India. Among all the predictive equations developed to estimate soil loss, the most accepted, used, convenient and suitable technique, for smaller areas like hillslopes and fields, is the Universal Soil Loss Equation (USLE). This method has been applied to the cultivated fields on either side of the gullied banks of the Adula and Mahalungi rivers, to estimate soil loss from fields under different crops. Rainfall data from the IMD has been used for the purpose. Field slope measurements, textural analysis of soil and determination of soil organic matter have also been carried out. Finally the soil loss has been computed from the generated data. The results have been used to ascertain whether the soil loss in the area is within or beyond the tolerance limit. It has been found that the soil loss in these areas have exceeded the tolerance limit and hence require due attention. 相似文献